Flow during production is regulated by a valve called a choke. The typical design for a choke comprises a body having a series of lateral ports and a sliding sleeve that has a matching port layout. A hydraulic system is used to move the insert sleeve in opposed directions. The hydraulic system also controlled the movement of the insert sleeve broadly in two different ways, both of which will be described in detail below.
In the J-slot design cycles of pressure application and removal made a pin follow a j-slot. A lug also on the movable member with the pin followed the pattern defined by the j-slot and with each cycle of application and removal of pressure the lug would encounter a different fixed travel stop that would define a different amount of percentage open for the valve. In one known design of the HCM-A choke offered by Baker Hughes Incorporated the j-slot allows the insert sleeve to go from a diffused position where it is not totally closed to various open positions with the j-slot pattern having two open passages to allow the lug an extra travel distance so that the valve could go to the fully open or fully closed positions.
In a modification to this valve the hydraulic control system was designed to move the insert sleeve a fixed amount for each pressure up cycle. Removal of the pressure in the second part of each cycle would simply leave the insert sleeve where it was and the next application of pressure would incrementally move the insert sleeve by an amount related to the displaced volume of a piston. Any time the pressure was applied to another control line the insert sleeve would go to the fully closed position.
The details of both these designs and their shortcomings that lead to the development of the present invention will now be described.
Referring to FIGS. 1 and 2, a valve housing 10 has control lines 12 and 14 that extend to opposite sides of piston 16. Piston 16 is connected to insert sleeve 18 for tandem movement. Insert sleeve 18 has a hole pattern 20 that moves up and down into and out of alignment with openings 22 in the housing 10. Seals 24 and 26 straddle ports 22 so that when openings 20 are not between seals 24 and 26 the valve is fully closed. On the other hand when the ports 20 are between seals 24 and 26, as shown in FIG. 1, then the valve is in the diffused position where some flow is possible between ports 20 and 22 through diffuser 28. Alternating pressure application between lines 12 and 14 forces relative movement of pin 30 in the j-slot pattern 32. A series of stair step travel stops 34 define how much more open the valve gets in each pressure cycle. The other half of each cycle has the lug 36 landing on the same spot 38 to define the diffused position shown in FIG. 1. In each pressure cycle, the lug 36 lands on a different step 34 to represent another opening increment. After a predetermined number of cycles the lug 36 can go to landing 40 for a fully closed position where the openings 20 are no longer between seals 24 and 26. In the very next cycle it can go to fully open when lug 36 is allowed to keep traveling by slot 41 until it hits stop 42.
This design does not allow the valve to always be closed with a single command. The design also usually requires multiple commands to reopen the valve after closure to a desired position. This mode of operation can result in additional wear on the ports 20 and 22. In some instances, operators wanted the ability to step the valve to different opening percentages but to also have the ability to snap it closed without having it go through any steps. The design in FIGS. 1 and 2 couldn't do this. What it could do is shown in FIG. 3. In each cycle it could open incrementally more and go to a diffused position where flow through it was fairly close to nothing. As a result a spike pattern of percent open was created and no provisions existed for a rapid close by skipping any part of the sequence illustrated in the j-slot of FIG. 2.
FIG. 4 represents a modification of the original design in FIGS. 1 and 2 that works on the principle of using a predetermined displaced volume to get a predetermined movement of an insert sleeve. Rather than going to almost closed in each cycle the insert sleeve just stays in position until the next cycle bumps it a finite amount proportional to the displaced hydraulic fluid volume. Another feature of this system is that it can be taken to closed immediately by applying pressure on one of the control lines.
The design in-FIG. 4 includes the following components: Line 44 supplies opening pressure to the mechanism and is connected to lines 48 and 46. Line 48 supplies pressure to piston 50. Line 46 supplies pressure to plunger 76 which is connected to piston 74, lines 68, 66 and 90 furnish pressure from the control mechanism to the valve 62 to cause the valve to open. Line 92 furnishes pressure to the valve to cause it to close. Piston 50 is used to move the valve from the fully closed position to the diffused position (such as is shown in FIG. 1). Piston 74 is used to move the valve sequentially to different opening positions. Spring 84 causes piston 74 to move to the left when pressure is bled off of line 44. The surface 86 of plunger 76 allows fluid to bypass plunger 76 during its movement to the left.
The operation of this control system will now be described. Initial application of pressure to line 44 will transmit through line 48 causing Piston 50 to move to the right until it stops and seals at face 94. This causes fluid in chamber 64 to move through lines 66 and 90 causing valve 62 to move from the closed position to the diffused position. Continued application of pressure to line 44, which is also communicating through Line 46 with plunger 76, will now cause plunger 86 and piston 74 to move to the right compressing spring 84 and causing fluid in chamber 70 to move through lines 68 and 90 moving valve 62 from the diffused position to the first open position. At this point, elimination of pressure in line 44 will allow spring 84 to move piston 74 and plunger 76 to the left. The design of plunger 76 includes the surface 86 which allows fluid from lines 44 and 46 to bypass plunger 76 during this leftward movement. Piston 50 does not move and stays in contact with face 94. A second application of pressure to line 44 will communicate trough line 46 to plunger 76 causing it to again move to the right which induces fluid to flow from chamber 70, through lines 68 and 90 to valve 62, moving valve 62 from opening position number 1 to opening position number 2. This elimination and application of pressure to line 44 will cause the valve 62 to consecutively move to opening positions 3, 4, 5, etc.
Any time the above opening sequence is interrupted by elimination of pressure from line 44 combined with application of pressure to line 92, full closure of the valve 62 is achieved. During this closure, fluid is exhausted from valve 62 through line 90 to lines 68 and 66. The exhaust flow in line 68, along with aid of spring 84, cause piston 74 and plunger 76 to move fully to the left. The exhaust flow in line 66 will cause the piston 50 to mover fully to the left. Continued exhaust flow from valve 62 is through lines 90 and 66 to chamber 64 and then through check valves 54 and 52 to lines 48 and 44 which enables the exhaust flow to be vented to surface. Now the valve 62 is fully closed. Valve 62 can now be re-opened as described above by application of pressure to line 44. However, note that in order to return valve 62 to the previous open position (that is occupied before closure) may require multiple pressure applications to line 44. Note also that any gas present in chambers 70 and 64 may affect the ability of piston 74 and plunger 76 to move valve 62 accurately to the next open position.
The present invention presents a control system for a hydraulic control valve, for example, that allows incremental opening in steps by cycling pressure to an opening chamber. Removing pressure to the opening chamber sends the system into a neutral position. Applying pressure to a closing chamber closes the valve by moving the insert sleeve to the closed position. Reapplying pressure after closure on the opening side returns the valve to the position it was in before it was closed. On the other hand, cycling pressure on the closing chamber can allow the valve to be subsequently reopened at any smaller percentage opening than it was in before it was closed. To open the valve to an open percentage that is higher than open position it was in when it was closed, pressure cycles are applied to the opening line. A split j-slot is employed to cycle the valve incrementally toward greater percentage openings on one half of the j-slot while on the separate j-slot the cycling allows the valve to be positioned to subsequently open at a desired percentage opening while staying closed as the cycling takes place. The cycling at either of the separate j-slots allows a travel stop for the insert sleeve to be repositioned. In essence the j-slot cycling creates relative rotation in either direction to extend or retract a travel stop for the insert sleeve. Pressure applied to the opening chamber always urges the insert sleeve to move toward the movable travel stop. Pressure applied to the closing chamber always urges the insert sleeve toward its fully closed position away from the movable travel stop. These and other features of the present invention will be more readily apparent from a review of the description of the preferred embodiment and the associated drawings that appear below with the understanding that the claims set out the full literal and equivalent scope of the invention.